Steroidal acid compounds and method of obtaining the same



Patented May 22, 1945 s'riinoi'nAL Aoin COMPOUNDS AND METHOD or OBTAINING THE SAME Russell Earl 'Marker, State College, Pa., and Eugene L. Wittle, Detroit. Mich, assignors to Parke, Davis 8,; Company, Detroit, Mich, a corporation of Michigan No Drawing. Application August 3, 1940, Serial No. 351,146

6 Claims. (01. zoo-397.1) This invention relates to steroidal acid com- 4 pounds and methods of obtaining the same.

Accordingly, an object of this invention is the preparation of steroidal acid compounds having utility in the preparation of pharmaceutical substances. I

Another object of this invention is to afford a new and useful method for obtaining steroidal acid compounds having utility in the preparation of pharmaceutical substances.

A further object of this invention is to prepare etio-cholanic acids from pregnane compounds by methods giving high yields.

Other objects of this invention will be discerned on perusal of this specification and the appended claims.

For the preparation of pharmaceutical substances such as the sex and-cortical hormones it is often necessary to make use of etio-cholanic acid derivatives. These have the following formulae:

CH3 CH3 l C D where the symbol m represents 7L carbon-tocarbon double bonds in the AB portion of the steroid nucleus, 12 having one of the values 0, 1, 2 and 3, and where the symbol mY represents m substituents in the AB portion of the steroid nucleus, said substituents being selected from the class consisting of hydroxyl and groups hydrolyzable to hydroxyl, and m havingone of the values 0, 1, 2 and 3, the sum of m and 12 not exceeding the value 3. By substituents hydrolyzable to hydroxyl, we mean such substituents as acyl, 0-aralkyl, and halogen.

Hitherto these etio-cholanic, acid derivatives have been obtained, but only in poor yields, by various methods which depend on the oxidation of pregnane derivatives. According to the present invention a new method is employed for the preparation of these etio-cholanic acid deriva-- tives in high yields.

COOH

lows.

V In practicing our invention We proceed as fol- As a starting material we use a 2 0-keto-preg nane compound representable by the formula bon double bonds in the A-B portion of the able to hydroxyl, and 111. having one of the values 0, 1, 2 and 3, the sum of m and n not exceeding 3. The requirement that the sum of m and it should not exceed the value 3 is based on practical considerations, for While it is relatively easy to obtain or prepare pregnane compounds of this type from suitable sources such as urines, sterols, bile acids, and sapogenins, the obtainment or preparation of pregnane compounds more highly substituted in the 1A-B portion of the nucleus is 30 generally relatively difficult.

A ZO-keto-pregnane compound of the above indicated type is condensed with an aldehyde or an aliphatic ketone to give an intermediate condensation product of the following formula where the symbol nA represents 1i carbon-to-carbon double bonds in the AB portion of the steroid nucleus, 11 having one of the values 0, 1, 2 and 3, where the symbol mY represents m substituents in the A--B portion of the steroid nucleus, said substituents being selected from the class consisting of hydroxyl and groups hydrolyzableto hydroxyl, and m having one of the Values 0, 1, 2 and 3, the sum of m and. n not exceeding the value 3; where R1 is a member of the class consisting of aliphatic hydrocarbon radicals and hydrogen, and where R2 is a member of the class consisting of alkyl, aralkyl, and aryl. For practical reasons, arising from the fact that of ketones, those of the aliphatic series such as acetone, methyl ethyl ketone, and the like operate Acetyl-etio-lithocholic acid KOH; then acidity CH: CH;

COOH

etio-llthocholio acid Our invention may be further illustrated by the following examples:

Example 1 (a) To a solution of 1.0 g. of pregnanol-3-(e) one-20 and 500 mg. of benzaldehyde in 25 cc. of absolute ethyl alcohol is added at 25 and with shaking a solution of 600 mg. of sodium 15 cc.

best in the practice of our invention, we limit R2 l of absolute f After mixture a Stoodto alkyl radicals when R1 is an aliphatic hydroabqut 20 mmutes at 25-30 crystanme carbon radical. terial is formed throughout the solution. The

These condensation products we n 21 a1ky1 mixture is allowed to stand, however, undisturbed idene-ZO-keto-pregnane compounds. To prefor twenty-four w and t is {muted with pare the etio-cholanic acids any group in rings A ether shaken Vlgorously W1t h dllute hydro and B such as groups which ordinarily chloric acid. 'lhe ethereal layer 18 separated and readily oxidize, are first intermediately protected Washed Wen Water and f' Potasslum against oxidation by treatment with a halogenatbonate solutlonon evaporatmg most of f ing, acylating or alkylating agent. Likewise, nuh product crystaulzes after coolmg clear double bonds are protected by addition of 20 y be filtered off and Washed wlth ether- The hydrogen hande halogen' Then the nuc1ear yield is about 1 1 g. of 2l-benzal-pregnanol-3-(a) 1y protected 21 alkylidene-ZO-keto pregnane one-20 of melting po1nt228-230 C. The product compounds are oxidized, preferably at higher may be readily crystallized from ethyl alcohol temperatures such as 50-100 0., with a strong when'thus ifi d melts at 230232 C. It IS oxidizing agent, such as an oxidizing agent se- 25 sparingly Soluble in acetone and ether- The lected from the group of compounds of hexavalent mother liq or can be concentrated to give a furchromium and heptavalent manganese, thereby ther quantity of the same compound. forming etio-cholanic acid derivatives. The acetate of 2l-benzal-pregnano1-3-(a)-onehis may be illustrated by the preparation of l 0 ay be p p y refluxing 1 of t p retio-lithocholic acid from pregnanol-3-(e)-oneent substance with 12 cc. of acetic anhydride for 20 according to the following equations: half an hour. Then the solution is evaporated i CH; C=CHCcHs CH: CH3 I CH: CHI &

I \J CaHuCHO V HOL/ (NaOEt) H0 V Pregnanol-3()-one-20 21-benzal-pregnanol-3(alone-20 Iii C=CHCt l 0 CH: CE:

coon /o=o to dryness in vacuo and the residue crystallized from acetone. The acetate is crystallized as thick plates from acetone. It melts at 152 C.

(b) To a solution of 800 mg. of 2 1-benzal-pregnanol-3-(e) -one-20 acetate of melting point 152" C. in 100 cc. of glacial acetic acid at 50' i added with stirring, over a period of half an hour, a solution of 1.5 g. of chromic. anhydride in 5 cc. of water and 50 cc. of acetic acid. The solution is stirred at 50-70". C. for 5 hours and then cc. ofalcohol is added to destroy the excess chromic anhydride. Thesolution then is concentrated in vacuo to cc., diluted with water and the mixture extracted with ether. The ethereal layer is separated, washed several times with water and then extracted with dilute potassium carbonate solution. The aqueous potassium carbonate extracts are combined, acidified with hydrochloric acid and the precipitated acid extracted with ether. The ethereal solution thus obtained is washed with water and evaporated to dryness and the crystalline residue recrystallized from dilute methanol to give acetyl-etio-lithocholic acid of melting point 226-228 C. The mother liquor contains benzoic acid of melting point 12'0-122 C. Since acetyl-etio-lithocholic acid is not a very strong acid it is not completely extracted from ethereal solution by means of potassium carbonate solution. Accordingly the ethereal layer from the above potassium carbonate extract is evaporated to dryness and the residue crystallized from acetone to yield the same acetyl-etio-lithocholic acid of melting point 230-232 C. The amount of acid thus obtained from the ethereal phase is about eight times as great as that obtained from the potassium carbonate phase. The total yield approximates 70%.

(c) A solution of 50 mg. of the acetyl-etio-lithocholic acid, prepared as described above in cc. of 2% alcoholic potassium hydroxide solution is heated to refluxing for one-half hour. Then it is poured into 200 cc. of water and this solution madeacid with dilute hydrochloric acid. The white solid acid which precipitates is extracted with ether and the ethereal solution washed with water and evaporated to a small volume, whereupon the acid crystallizes. The acid is recrystallized from acetone to give etiolithocholic acid of melting point 275-278 C,

(d) This acid may be oxidized at 20 by treatment with an equal weight of chromic anhydride in acetic acid to give 3-keto-etio-cholanic acid of melting point 246-249 C.

Example 2 (a) To a solution of 1.0 g. of pregnanol-S-(s) one-20 acetate and 500 mg. of benzaldehyde in 15 cc. of absolute alcohol is added a solution of 600 mg. of sodium in cc. of alcohol. In about fifteen minutes crystals are formed throughout the solution. The solution, however, is allowed to stand for twenty-four hours undisturbed. Then it is diluted with ether and washed with dilute hydrochloric acid. The ethereal layer is separated, washed with Water and dilute sodium carbonate solution and evaporated almost to dryness. The product which crystallizes from the ether is collected and washed with ether to give the crude product which has the melting point of 1'721'75 C. After several recrystallizations from acetone the pure 2l-benzal-pregnanol- B-(pl-one-ZO is obtained as white crystals of melting point 179 C.

During the course of the above condensation, the 3-acetoxy group is hydrolyzed. To prepare the acetate of 2lbenzal-pregnanol-3-(,B) -one20 the parent compound is refluxed withaboutv 15 times its weight of acetic anhydri-de for about half an hour. Then the solution is evaporated to dryness under reduced pressure and the residue is crystallized from acetone. In this mannor there is obtained the acetate of 21-benzalpregnanol-3-(m-one-20 as crystals of melting point 175 C. This depresses with the parent benzal compound to 150-155 C. showing their non-identity.

(b) The acetate of 21-benzal-pregnano1-3-(B) one-20 may be oxidized in a manner similar to that described in Example 1 to give 3-(fl) -hydroxy-etio-cholanic acid. The purified product after hydrolysis and crystallization from dilute acetone has a melting point of 229-230 C. When treated with ethereal diazomethane it forms a methyl ester which after crystallization from di lut acetone or methanol melts at BB -142 C. The 3-(p)-hydroxy-etio-cholanic acid" may be treated with pyridine and acetic anhydride and worked up in the known manner to give the anhydride-acetate of melting point 188-190 (0) Under mild conditions of oxidation 3-(5) hydroxy-etio-cholanic acid may be oxidized to give S-keto-etio-cholanic acid identical with that obtained by oxidizing 3-(11) -hydroxy-etio-cholanic acid (etio-lithocholic acid). This shows that the 3-hydroxy-etio-cholanic acid of this example and Example 1 are epimeric about 0-3.

To a solution of 300 mg. of 3(5) -hydroxy-etiocholanic acid in cc. of acetic acid at 20 is added a solution of 200mg. of chromic anhydride in 20 cc. of acetic acid. The solution is allowed to stand at room temperature for one hour and then is diluted with water and the product extracted with ether. The ethereal solution is washed thoroughly with water and evaporated to dryness. The residue is crystallized from acetone to give 3-keto-etio-cholanic acid of melting acid of melting point 202-204 C. is obtained.

(a) To a solution of 500 mg. of epi-al1o-pregnanol-3-one20 and 600 mg. of benzaldehyde in 30 cc. of absolute ethyl alcohol is added at 25 a solution of 700 mg. of sodium dissolved in 15 cc. of absolute ethyl alcohol. After the mixture has stood at room temperature for 24 hours it is poured into water and the mixture extracted with ether. The ethereal layer is separated and shaken with dilute hydrochloric acid and then with water. The ethereal extract is evaporated to dryness to leave an oily residue which resists crystallization. This is the 21-'benzal-allo-pregnanol-3- (a) -one-20.

(b) i This oil is dissolved in acetic anhydride an refiuxed for one hour. Then it is evaporated to dryness under reduced pressure and the residue dissolved in 100 cc. of acetic acid. To this solution at 95 C. is added with stirring a solution of 2 grams of chromic anhydride in 50 cc. of 95% acetic acid. After the solution has stood at 95 for two hours it is diluted with water and extracted with ether. The ethereal layer is separated and washed with water and dilute sodium bicarbonate solution, and then with 5% potassium hydroxide solution. The potassium hydroxide extract is heated on the steam bath for onehalf hour, cooled, acidified and extracted with ether. The ethereal extract thus obtained is evaporated to dryness and the residue crystallized repeatedly from dilute methanol to give 3- (c) -hydroxy-etio-allo-cholanic acid of melting point 282-285 C.

On treatment with acetic anhydride and, pyridine there is obtained from this 3-(oz) -hydroxyetio-allo-cholanic acid a compound which is apparently an acetate-anhydride. It may be crystallized from methanol to a constant melting point of 208-210 C.

Instead of using a 3-hydr0Xy-pregnanone-2O compound according to these examples one may substitute other analogous compounds such as the 3-enol-ethers of progesterone, 3-chloro-pregnanone-ZO, or A -pregnenol-3-(fi)-one-20 to obtain the corresponding benzal derivative. In each case these compounds may be oxidized according to the method given in the above example to obtain the etio-cholanic acid derivative. For example, there is obtained by the oxidization of the 3-enol ethyl ether of 21-benzal progesterone, the 3-enol ethyl ether of 3-keto-M-etio-cholenic acid. Likewise, there is obtained from the 21- benzal derivative of 3-chloro-pregnanone-20,'on oxidation with chromic acid at 95 C., the 3- chloro-etio-cholanic acid. Again the benzal derivative of A -pregnenol-3-(p) -one-20 may be oxidized with chromic acid at elevated temperature, with intermediate protection of the 3-OII group by acetylation and of the double bond by addition of bromine, to give the 3-(,B)-hydroxy-A etio-cholenic acid.

The above examples illustrative of our invention are capable of a number of variations in regard to the reagents and conditions employed, and these variations will be apparent to those skilled in the art, in view of this disclosure. Accordingly we do not wish our invention to be limited to any specific embodiment of this invention.

For example, instead of using benzaldehyde in the condensation to form the 2l-alkylidene compounds we may use other aldehydes or reactive lower aliphatic ketones such as acetaldehyde, trimethylacetaldehyde, anisaldehyde, isovaleraldehyde acetone, ethylmethyl ketone, diethyl ketone and the like. Also instead of using sodium ethylate or a solution of sodium in alcohol as the alkaline condensing agent we may use other alkaline condensing agents such as sodamide, potassium ethylate, potassium methylate, sodium metal in ether, and other combinations selected from the class consisting of alkali metals and the amides and alcoholates thereof. Instead of using chromic anhydride in acetic acid as an oxidizing agent We may use the combination of potassium dichromate in sulfuric acid, or potassium permanganate in sulfuric acid, or other combinations employing oxidizing agents selected from the group of compounds of hexavalent chromium and heptavalent manganese. For protecting nuclear hydroxyl groups, we may use acylating agents such as acetic anhydride, phthalic anhydride, benzoyl chloride and the like. Or we may use alkylating agents such as benzyl chloride, triphenylmethyl chloride, or other etherifying agents. Again we may protect nuclear hydroxyl groups by temporary halogenation with a reagent such as phosphorus pentachloride or thionyl chloride, subsequently removing the chlorine atom by hydrolysis as for example by refluxing the haloetio-cholanic acid derivative with potassium acetate in acetic acid.

It is apparent that our invention also embodies a new group of substances which we designate as 21 alkylidene 20 keto pregnane compounds. These have the formula:

where the symbol nA represents 11 carbon-to-carbon double bonds in the AB portion of the steroid nucleus, it having one ,of the values 0, 1, 2 and 3, where the symbol mY represents m substituents in the A -B portion of the steriod nucleus, said substituents being selected from the class consisting af hydroxyl and groups hydrolyzable to hydroxyl, and m having one of the values 0, 1, 2 and 3, the sum of m and n not exceeding the value 3; where R1 is a member of the class consisting of aliphatic hydrocarbon radicals and hydrogen, and where R2 is a member of the class consisting of alkyl, aralkyl, and aryl and where R1 is an aliphatic hydrocarbon radical, R2 is alkyl.

What we claim as our invention is:

l. The process of preparing steroidal acid compounds which comprises condensing a 20- keto-pregnane compound with a member of the group consisting of aldehydes and reactive lower aliphatic ketones in the presence of an alkaline condensing agent thereby forming a 21-alky1- idene 20 keto pregnane compound, oxidizing said 21-alkylidene-20-keto-pregnane compound with intermediate protection of groups in the steroid nucleus, said oxidation being carried out at 50 to C. with an oxidizing agent selected from the class consisting of compounds of hexavalent chromium and heptavalent manganese thereby forming an etio-cholanic acid derivative, removing the protecting groups, and isolating the etio-cholanic acid derivative.

2. The process of preparing steroidal acid com-, pounds which comprises condensing a 20-ketopregnane compound of the formula steroid nucleus, 11 having one of the values 0, 1, 2 and 3, and where the symbol mY represents m substituents in the A-B portion of the steroid nucleus, said substituents being selected from the class consisting of hydroxyl and groups hydrolyzable to hydroxyl, 112 having one of the values 0, 1, 21 and 3, the sum of m andn not exceeding the value 3, with a member of the group consisting of aldehydes and lower reactive aliphatic ketones in the presence of an alkaline condensing agent thereby forming a 21-alkylidene-ZO-keto-pregnane compound, oxidizing said 21-alkylidene-20-keto-pregnane compound with intermediate protection of groups in the steroid nucleus, said oxidation being carried out at 50 to 100 C. with an oxidizing agent selected from the class consisting of compounds of hexavalent chromium and heptavalent manganese thereby forming an etio-cholanic acid derivative, removing the protecting groups and isolating the etio-cholanic acid derivative.

3. The process of preparing steroidal acid compounds which comprises condensing a ZO-ketopregnane compound with an aromatic aldehyde in the presence of an alkali metal alcoholate thereby forming a 21-alkylidene-ZO-keto-pregnane compound, protecting any nuclear hydroxyl groups by treatment with an acylating agent, and protecting any nuclear double bonds by treatment with a reagent selected from the class consisting of hydrogen halides and halogens, oxidizing said protected 21-alkylidene-20-keto-preg- I nane compound with chromic acid at 50 to 100 C. thereby forming an etio-cholanic acid derivative, removing the protecting groups and isolating where Y is selected from the class consisting of OH and -Oacyl, with an aromatic aldehyde in the presence of an alkali metal alcoholate thereby forming a compound of the formula protecting the nuclear hydroxyl group by treatment with an acylating agent, oxidizing said protected compound with chromic acid at to C. thereby forming a 3-acyloxy-etio-oholanic acid, removing the acyloxy group by hydrolysis, and isolating the 3-hydroxy-etio-cholanic acid.

5. The process of preparing steroid'al'acid compounds which comprises condensing a compound of the formula Where Y is selected from the class consisting of -OH and -O--acyl, with an aromatic aldehyde in the presence of alkali metal alcoholate thereby forming a compound of the formula 11 H CH3 CH3 C/ aryl protecting the nuclear hydroxyl group by treatment with an acylating agent, and protecting the nuclear double bond by treatment with a reagent selected from the class consisting of hydrogen halides and halogens, oxidizing said protected compound with chromic acid at 50 to 100 C. thereby forming an etio-ch-olanic acid derivative, removing the protecting groups, and isolating the 3-hydroXy-A -etio-cholenic acid.

6. The step of oxidizing a 21-alkylidene-20- keto-pregnane compound with intermediate protection of groups in the steroid nucleus, said oxidation being carried out at 50 to 100 C. with an oxidizing agent selected from the class consisting of compounds of hexavalent chromium and heptavalent manganese thereby forming an etio-cholanic acid derivative.

RUSSELL EARL MARKER. EUGENE L. WI'ITLE. 

